<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body{
            margin: 0;
        }
        /**{margin: 0}*/
        h1,p,ul{margin: 0}
        ul{padding: 0}
        #d1 {
            width: 400px;
            height: 200px;
            border: 10px inset red;
            /* border-bottom: 10px solid red;
             border-right: 10px solid red;*/
            /*设置圆角*/
            border-radius: 200px;
        }

        #d2 {
            width: 100px;
            height: 100px;
            border: 1px solid blue;
            /*给元素添加内边距 默认会影响元素的宽高*/
            padding-left: 50px;
            padding-top: 50px;

            /*添加这个样式后 内边距和边框则不再影响宽高*/
            box-sizing: border-box;
        }

    </style>
</head>
<body>
<input type="text">
<h1>这是h1</h1>
<p>这是p标签</p>
<ul>
    <li>aaa</li>
    <li>bbb</li>
    <li>ccc</li>
</ul>
<div id="d2">
    内边距
</div>
<div id="d1">边框</div>
</body>
</html>